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Published on: August 1, 2018
Anatomy of hierarchy: feedforward and feedback pathways in macaque visual cortex
Nikola T Markov1, Julien Vezoli, Pascal Chameau
1Stem Cell and Brain Research Institute, INSERM U846, 69500, Bron, France; Université de Lyon, Université Lyon I, 69003, Lyon, France; Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut, 06520-8001, USA.
The Journal of Comparative Neurology
|August 29, 2013
Summary
Cortical hierarchies are organized by distinct feedforward and feedback pathways. These pathways, segregated into supragranular and infragranular layers, form dual counterstreams enabling directed connectivity.
Area of Science:
- Neuroscience
- Systems Neuroscience
- Computational Neuroscience
Background:
- Cortical hierarchical organization is determined by the laminar location of neuronal connections.
- Understanding the principles of feedforward (FF) and feedback (FB) pathways remains limited.
Purpose of the Study:
- To investigate the connectional principles of FF and FB pathways using laminar distribution of neurons.
- To refine models of cortical hierarchy and explore areal relationships.
Main Methods:
- Quantitative analysis of retrograde tracers to determine supragranular labeled neurons (SLN).
- Cell filling techniques to visualize parent neurons of FF and FB pathways.
Main Results:
- SLN values provide insights into hierarchical distance and reveal unexpected areal relationships.
- Supragranular layers host segregated bottom-up and top-down streams with point-to-point connectivity.
- Infragranular layers contain diffuse bottom-up and top-down streams, indicating compartmentalization.
- FF pathways exhibit higher weights, fewer hierarchical levels crossed, and lower numbers compared to FB pathways.
Conclusions:
- Cortical hierarchies are constructed from segregated supra- and infragranular counterstreams.
- This dual counterstream organization facilitates compartmentalized point-to-point connectivity in both bottom-up and top-down directions.
Related Concept Videos
01:24Vision
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01:14Motor and Sensory Areas of the Cortex
The cerebral cortex, the brain's outermost layer, is pivotal in processing complex cognitive tasks, emotions, and various sensory inputs and executing voluntary motor activities. This intricate structure is divided into three primary functional areas: the motor areas, sensory areas, and association areas.
Motor Areas
The motor areas located in the frontal lobe are central to controlling voluntary movements. This region is further subdivided into the primary motor cortex and the premotor cortex.
Motor Areas
The motor areas located in the frontal lobe are central to controlling voluntary movements. This region is further subdivided into the primary motor cortex and the premotor cortex.
01:26Visual System
Light enters the eye through the cornea, a transparent, dome-shaped surface covering the surface of the eyeball that helps to direct and focus incoming light. This light is then channeled toward the pupil, an adjustable opening whose size is controlled by the iris. The iris, a pigmented muscle, regulates the amount of light entering the eye by contracting or dilating the pupil, thereby ensuring optimal light levels for clear vision.
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01:18Hierarchy of Motor Control
The hierarchy of motor control refers to the different levels of organization and processing involved in controlling movement in the body. These levels range from higher cortical areas involved in planning and decision-making to lower spinal cord reflexes that respond automatically to external stimuli.
01:32The Retina
The retina is a layer of nervous tissue at the back of the eye that transduces light into neural signals. This process, called phototransduction, is carried out by rod and cone photoreceptor cells in the back of the retina.
01:21Association Areas of the Cortex
Association areas are regions of the cerebral cortex that do not have a specific sensory or motor function. Instead, they integrate and interpret information from various sources to enable higher cognitive processes such as memory, learning, and decision-making. Some key association areas include the following:
Prefrontal Association Area: This area is located in the frontal lobe and is involved in planning, decision-making, and moderating social behavior. It connects with primary motor areas,...
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